How to Make an Herb Spiral

Potted herb transplants are easiest to establish in an herb spiral.

An herb spiral, besides providing a bounty of kitchen herbs, is a striking landscape feature and garden space-saver. Typically taking up less than 25 square feet, the structure's stacked profile allows you to double your growing space. Just as importantly, a rock- or brick-enclosed spiral creates several microclimates, from the center and highest point in elevation of the spiral and downwards. This makes it possible to grow herbs close together that have varying drainage, moisture and sunlight needs. The top of the spiral is best for sun and drought-tolerant herbs, while the unspooling row becomes gradually moister and shadier.

1

Clear an area at least 7 or 8 feet in circumference. This clearance allows room for the spiral and keeps the outside edges free of weeds.

2

Set cardboard or newspaper over the area to suppress weeds.

3

Lay down a softened hose or stakes and string to create a flat outline of a spiral. This will indicate where the first layer of rocks or bricks will go. The spiral should be about 5 feet in diameter. Traditionally, the outer tail end of it should be on the northern side of the structure, and it will be one rock or brick high. The spiral gains height as it gradually coils inward to its center-most point, which will be four to five rocks or bricks high.

4

Place your rocks or bricks to form the lowest level of the spiral, starting with the outer tail and working to the innermost spiral. If you are using building blocks of different sizes, the largest rocks or bricks should go down first to build up the lowest tier.

5

Set a 2-inch layer of gravel at the bottom of the spiral to improve drainage.

6

Set a 50-50 mixture of compost and topsoil over the gravel until it is almost level with the first course of stones or bricks. The soil mix, which you need as a planting medium, also helps stabilize the structure as it is being built.

7

Start a second layer of rocks or bricks. This time, start the second tier indented several feet from the end of the outer "tail" of the spiral.

8

Place more of the soil mix down, between the rows of rocks or bricks, after finishing the second course of rocks.

9

Continue building up the spiral using rocks or bricks, with the soil mix between these rows of blocks. When completed, the outermost end of the coil will be 6 to 8 inches high, gradually coiling upward so that the highest point is in the center, and about 3 feet high tall. Depending on the size of your building materials, the inner wall may consist of four to five bricks or rocks, gradually lowering to the outer tail, which is one rock or brick tall.

10

Close the outer tail of the spiral by setting stones or bricks at the end to prevent dirt and water erosion until the plants are established.

11

Water the topsoil and allow to settle for one or two days.

12

Set sun-loving, drought-tolerant herbs in the inner, highest section of the spiral. These include such traditional Mediterranean herbs as thyme (Thymus vulgaris, U.S. Department of Agriculture plant hardiness zones 5 to 9) and rosemary (Rosmarinus officinalis, USDA zones 8 to 10).

13

Plant your most shade-tolerant, moisture-loving herbs at the lowest section of the spiral, on the north side. Good choices for this section include chives (Allium schoenoprasum), hardy in USDA zones 4 to 8, and mints such as apple mint (Mentha suaveolens), hardy in USDA zones 5 to 9.

14

Fill in the rest of the spiral according to the herbs' general needs. Basil (Ocimum basilicum), hardy in USDA zones 2 to 11, prefers sun and even moisture; a space on the sunny side of the wall on the middle section might serve it well. Good candidates for the middle tier on the eastern or western sides include the part-shade loving "Walker's Low" (Nepeta racemosa "Walker's Low"), also known as dwarf catmint, which thrives in USDA zones 4 to 8.

15

Put a 1-inch layer of mulch around the herbs. Finely-ground wood chips, cocoa pellets or other small-sized materials are ideal.

16

Finish the outer edges at the base of the herb spiral by setting down mulch or gravel. This acts as a circular path to access the spiral at all angles, while also keeping weeds away from the structure.

Things You Will Need

Cardboard or newspaper

Old garden hose, stakes and string or other marking materials

About 100 bricks or rocks

Gravel

Topsoil

Compost

Tip

While most herbs do best in the medium-rich soil provided by the topsoil-compost mixture, some plants can benefit from the addition of soil amendments. Add them as you establish your plantings. For example, a spadeful of sand can improve drainage at the top of the spiral where thyme and other Mediterranean plants thrive. Basil, which likes rich soil, may benefit from extra compost or manure.

Some gardeners set a stone at the tail end of the herb spiral to prevent dirt erosion. Others leave it open and put a small pool or sunken hole at the end of the spiral to create a bog-like area for plants that prefer wet feet.

Warning

Review nursery labels carefully, especially for spacing suggestions. Dealing with over-crowded plants can be tricky in a space as intricately-planted as an herb spiral.